Control of reversible induction motor drives

DURING the past several years, saturable reactors and self-saturating magnetic amplifiers have found increasing application for the control of reversing induction motor drives for intermittent slow-speed duty. The restriction to intermittent duty is imposed by the low motor efficiency at slow speed. With speed feedback, which is usually included, the reactor-controlled induction motor possesses adjustable speed characteristics and speed-torque curves similar to those of a d-c adjustable voltage drive. The minimum no-load speed is about 1 per cent, and the speed drop between no load and full load is in the order of 5 to 10 per cent of synchronous speed.